Various kinds of known panel retention structures are provided (for example, JP2007-203862A (hereinafter referred to as Patent reference 1)). The panel retention structure disclosed in Patent reference 1 includes a resin-made roof panel forming a design surface, and a metal-made base panel supporting the roof panel. The roof panel and the base panel are joined with each other by glue made of, for example, urethane resin, which is disposed therebetween.
Here, the joint of the roof panel and the base panel by glue may cause a problem in which the roof panel is separated from the base panel in a case where the glue is removed by, for example, adhesive failure or the effect of vibration when a vehicle runs at high speed.
Now, the roof panel is retained relative to the base panel with the use of a retention member (clip) in addition to glue. FIG. 9 shows a cross sectional view illustrating an example of the retention structure of the retention member. As illustrated in FIG. 9, the resin-made roof panel 90 includes a panel body 91 forming the design surface and a retention portion 92 protruding downwardly relative to the panel body 91. The retention portion 92 includes a retention wall 92a extending along the panel body 91. The retention wall 92a includes a first hole 92b opening in a vehicle height direction.
Meanwhile, the metal-made base panel 95 includes a second hole 95a facing the first hole 92b and opening in the vehicle height direction below the retention portion 92. The second hole 95a opens larger than the first hole 92b so as to include the whole first hole 92b therewithin.
The retention member 97 includes a neck portion 97a being inserted into the first and second holes 92b, 95a. The retention member 97 includes a first head portion 97b and a second head portion 97c. The first head portion 97b is connected to an upper end of the neck portion 97a provided in the first hole 92b and is in contact with a circumferential rim portion of the first hole 92b. The second hole 95c is connected to a lower end of the neck portion 97a provided in the second hole 92a and is in contact with a circumferential rim portion of the second hole 95a. The retention member 97 retains the roof panel 90 relative to the base panel 95 by sandwiching the retention wall 92a and the base panel 95 between the first and second head portions 97b, 97c. 
Meanwhile, the retention member 97 sandwiches the retention wall 92a and the base panel 95 between the first and second head portions 97b, 97c to fix the roof panel 90 and the base panel 95 in the vehicle height direction. Thus, because the joint position joined by glue is unchanged, the retention member 97 may draw in the retention portion 92, and the panel body 91 may be deformed in a case where the roof panel 90 is thermally deformed in accordance with the change in temperature.
A need thus exists for a panel retention structure which is not susceptible to the drawback mentioned above.